Cyclohexyl-aromatic hydrocarbon



Aug. 14, 1934. F. MARTl N ET A; 1,969,984

CYCLOHEXYL AROMATIC HYDROCARBON Filed May 51, 1932 MOZGJ AZ 0Z per Molefiyclahexene INVENTORS Zawrenas Emrtzln BY Gerald E 6'0Zernamu PatentedAug. 14, 1934 UNITED STATES CYCLOHEXYL-AROMATIC HYDROCARBON Lawrence F.Martin and Gerald H. Coleman, Midland, Micl 1., assignors to The DowChemical Company, Midland, Mich.,' a corporation of Michigan 3 Claims.

The present invention concerns an improved method of reactingcyclohexene with aromatic hydrocarbons, particularly with chlorinatedaromatic hydrocarbons, to obtain the monocyclohexyl derivatives of thelatter in relatively high yield.

The present application is a continuation in part of our priorapplication, Serial No. 424,443, filed January 29, 1930, for Halogenatedaliphaticaromatic hydrocarbons and method of making same.

It is known that cyclohexene may be reacted with various aromatichydrocarbons (e. g. benzene, xylene, etc.) in the presence of aconsiderable quantity of aluminum chloride (i. e. at least 0.3 molofaluminum chloride for each mol of cyclohexene used) to form thecorresponding monocyclohexyl aromatic hydrocarbons. The general type ofreaction involved may be represented by the following equation for theformation of monocyclohexyl-benzene from benzene and cyclohexeneHowever, in preparing a monocyclohexyl-aromatic hydrocarbon according tosuch usual method, a considerable portion of the reactants employed arelost through the formation of byproducts, e. g. polycyclohexyl-aromatichydrocarbons, so that the desired monocyclohexyl-aromatic hydrocarbon isobtained in relatively low yield.

We have now found that, if cyclohexene is reacted with an aromatichydrocarbon in the presence of a materially smaller quantity of aluminumchloride or corresponding aluminum halide than that heretofore used,preferably between about 0.02 and about 0.25 mol of aluminum halide permol of cyclohexene used, a monocyclohexyl-aromatic hydrocarbon isproduced in much higher yield, the relative quantity of by-products, e.g. polycyclohexyl-aromatic hydrocarbons, formed during reaction beingreduced to a corresponding extent. We have found, furthermore, that theemployment of such relatively small quantity of aluminum halide isparticularly advantageous in reacting cyclohexene with a chlorinatedaromatic hydrocarbon, in that the relative yield of the desiredmonocyclohexyl-chlorinated aromatic hydrocarbon is increased to anespecially great extent over the yield obtainable when the reaction iscarried out under similar operating conditions in the presence of arelatively large quantity of the same aluminum halide as a catalyst.

To the accomplishment of the foregoing and related ends, our inventionconsists of the method hereinafter fully described and particularlypoint ed out in the claims, the following description Application May31, 1932, Serial No. 614,410

and the accompanying drawing setting forth in detail several of thevarious ways in which the principle of our invention may be used.

In the accompanying drawing, Fig. 1 is a graph showing the yields ofmonocyclohexyl-chlorobenzene obtained through reacting cyclohexene withmonochloro-benzene in the presence of various'quantities of aluminumchloride as catalysts, the quantities of the latter being expressed asmols of aluminum chloride per mol of cyclohexene used. Curve A of Fig. 1represents the yields of monocyclohexyl-chlorobenzene obtainable throughemploying monochlorobenzene and cyclohexene in a molecular ratio of 3mols of the former reactant to 1 mol of the latter, the reactions beingcarried out in the presence of the quantities of aluminum chlorideindicated and at a temperature between and C. Curve B of Fig. 1represents data collected from runs made under similar operatingconditions except that monochlorobenzene and cyclohexene were employedin a molecular ratio of 5 mols of the former compound to 1 mol of thelatter.

From Fig. 1 two principles, which we have found to be general for thereaction of cyclohexene with aromatic hydrocarbons (e. g. benzene,toluene, xylene, naphthalene, diphenyl, monochlorobenzene,ortho-dichlorobenzene, monochlorodiphenyl, etc.) as a class, may beobserved, viz.; (1) for a given ratio of an aromatic hydrocarbon tocyclohexene and for a given reaction temperature, yields are maximumwhen between about 0.02 and about 0.25 mol of an aluminum halide per molof cyclohexene is used in carrying out the reaction; (2) for a givenratio of an aluminum halide to cyclohexene and for a given reactiontemperature, yields of the monocychlohexyl-aromatic hydrocarbon productbecome higher as the molecular ratio of aromatic hydrocarbon tocyclohexen is increased. The second of the above generalizations holdswithin the ranges which have been tested and within the ranges whichwould be employed in carrying out such reaction on a commercial scale.In practicing our invention we prefer to employ between about 3 andabout '7 mols of aromatic hydrocarbon for each mol of cyclohexene usedand we find it most advantageous to employ between 5 and 6 mols of thearomatic hydrocarbon for each mol of cyclohexene used.

The following table of examples sets forth the operating conditionsemployed and the yields of monocyclohexyl-aromatic hydrocarbons obtainedthrough reacting cyclohexene with aromatic hydrocarbons in the presenceof various quantities of aluminum chloride as catalyst. It is to beunderstood that said examples are illustrative of but several of thevarious Ways in which the principle of the invention may be used and arenot to be construed as a limitation on the invention.

The procedure described below was employed in carrying out theexperiments described in the table of examples.

Into a 3 necked, round bottom flask provided with a mechanical stirrer,a dropping funnel, and a reflux condenser fitted with a drying tubecontaining calcium chloride, were placed the desired quantities ofaluminum chloride and an arcmaticv hydrocarbon. The mixture was thenstirred while the desired quantity of cyclohexene was slowly introducedthereto by means of the dropping funnel. The reaction usually startedimmediately upon introducing the cyclohexene to the mixture, thetemperature rising spontaneously during reaction and being controlled byregulating the rate of introduction of cyclohexene. After all of thecyclohexene had been admitted to the mixture, stirring was continued,usually for about 15 minutes, and then cooled to room temperature andpoured into 1 liter of an aqueous solution containing 50 cubiccentimeters of'concentrated hydrochloric acid. After shaking thoroughlywith the dilute acid solution, the organic layer was separated, dried,and fractionally distilled to separate-the monocyclohexyl-aromatichydrocarbon in substantially pure form. In some instances the finalfractional distillation step was preceded by a steam distillation of thecrude reaction mixture to separate relatively volatile unreactedcompounds therefrom, but such steam distillation step is in no casenecessary as the unreacted materials may be separated from the desiredproducts by fractionally distilling the mixture in the usual way.

In the following table of examples, the percentage yields listed are thepercentage yields of monocyclohexyl-aromatic hydrocarbon products, basedon the quantities of cyclohexene employed in preparing said products.Also, in those experiments marked 500 0.0. of CS2, the reactions wereeach carried out in the presence of 500 cubic centimeters of carbonbisulphide as a reaction solvent.

going table of examples, it may be seen that when cyclohexene and anaromatic hydrocarbon, which may or may not be substituted by chlorine,are employed in a given molecular ratio and. are reacted in the presenceof aluminum chloride at a given temperature, the yield of monocyclohexylproduct formed is dependent, for the most part, upon the relativequantities of aluminum chloride and cyclohexene employed. The yield ishighest when between about 0.02 and about 0.25 mol of aluminum chlorideis employed for each mol of cyclohexene used. A comparison of curve Awith curve B in Fig. 1 of the accompanying drawing and a comparison ofexperiments 1 to 6 with experiments 9 to 13 in the table of examplesshows that when aluminum chloride and cyclohexene are employed in agiven molecular ratio and comparative reactions are carried out atsubstantially the same temperature, the yield of monocyclohexyl-aromatichydrocarbon product becomes higher as the molecular ratio of thearomatic hydrocarbon reactant to cyclohexene is increased. The lastmentioned generalization holds accurately up to a molecular ratio ofabout '7 mols of hydrocarbon to about one mol of cyclohexene used andapparently also holds true at higher ratios. The two generalizations setforth above are of fundamental importance in carrying out a reactionbetween cyclohexene and an aromatic hydrocarbon and hold rigidly for allaromatic hydrocarbons capable of being reacted with cyclohexene in thepresence of aluminum chloride.

Comparative experiments 7, 8 and 9, in the table of examples, illustratefurther the second generalization mentioned above, viz.:--that for agiven molecular ratio of aluminum chloride to cyclohexene, the yield ofmonocyclohexyl aromatic hydrocarbon product becomes higher as themolecular ratio of the aromatic hydrocarbon to cyclohexene is increased.A comparison of run 22 with run 23 illustrates the fact that thisgeneralization holds true, even when an inert solvent, e. g. carbonbisulfide, is employed in carrying out the reaction.

Comparative experiments 18, 19, and 20, in the Table of examples Organichydrocarbon Mol ratio M01 ratio 01- Reaction Expt. Mols of Mols oi of rPercent- No. cm. 1101, A101. a l igg: age yield Remarks Compound Mols061110 1 1. 0 Monochlorobenzene.-. 3. 0 0. 010 0.010 3. 0 -30 'Noreaction. 2 l. 0 -d0 3. 0 0.025 0.025 3.0 35-45 57. 8 3 l. 0 -d0 3. 0 0.050 0.050 3.0 35-45 64. 5 4 1. 0 -.-...(lo 3. 0 0.550 0.550 3.0 35-4534. 5 5 1.0 do 3.0 1.100 1.100 3.0 35-45 23.3 6 1. 0 ----do 3. 0 l.100 1. 100 3.0 130-135 13. 6 7 1. 0 --(l0- 2. 0 0. 025 O. 025 2.0 35-4544. 2 8 1. 0 do 4. 0 0. 025 0.025 4. 0 35-45 04. 7 9 1. 0 -.d0 5. 0 0.025 0. 025 5. 0 35-45 64. 9 i0 1. 0 do 5. 0 0. 050 0.050 5.0 35-45 77. 011 1. 0 d0 5. 0 0. 025 0. 025 5. 0 38-41 57. 3 1'. 1. 0 do 5. 0 0. 5000. 500 5. 0 -40 45. 0 13 1. 0 0.- 5.0 1. 000 1. 000 5.0 -45 34. 1 14 1.0Ortho-drchloro-ben- 5.0 0.100 0.100 5.0 38-42 46.5

zone. 15 0. 5 Ortho-chlorotoluene..- 2. 5 0. 050 0. 100 5. 0 39-40 59. 716 1. 0 Para-chlorodiphenyL. 2.0 0. 150 0. 150 2.0 27-41 61. 2 500 c.c.of CS1. 17 1. 0 Allpba-chloronaphtha- 5. 0 0. 100 0. 100 5. 0 20-40 54.8

e l8 1. O 3. 0 0. 010 0. 010 3.0 -50 31. 7 l9 0. 5 1. 5 0.050 0. 100 3.0 40-50 65. 8 20 1. 0 3. 0 1. 100 1. 100 3.0 40-50 33. 2 21 1.0 5.00.050 0.050 5. 0 89-43 78. 5 22 l. 0 1. 0 0.200 0. 200 1. 0 35-45 27. 1500 0.0. of CS1. 23 1.0 0 2.0 0.200 0.200 2.0 35-45 42.7 500 c.c. ofCS1. 24 0. 5 Diphenyl 2. 5 0. 025 0. 050 5. 0 38-39 66. 9 500 0.0. oiCS1. 25 l. 0 Toluene 5. 0 0. 050 0. 050 5. 0 38-42 80. 4

From Fig. 1 of the accompanying drawing and table of examples, furthersubstantiate one of from experiments 1 to 6 and 9 to 13 in the foretheforegoing generalizations and illustrate the fact that when cyclohexeneand benzene, in given molecular ratio, are reacted in the presence ofaluminum chloride, the yield of monocyclohexylbenzene product is highestwhen between about 0.02 and about 0.25 mol of aluminum chloride per molof cyclohexene is employed in carrying out the reaction. Comparison ofexperiment 19 with experiment 21 shows that when cyclohexene is reactedwith benzenein the presence of aluminum chloride and the molecular ratioof aluminum chloride to cyclohexene is held constant the yield ofmonocyclohexyl-benzene product becomes higher as the molecular ratio ofbenzene to cyclohexene is increased.

While, in the examples and in the foregoing generalizations, aluminumchloride has specifically been referred to as a catalyst, and while weprefer to employ aluminum chloride as a catalyst in practicing ourinvention, it shall be understood that the generalizations set forthabove are applicable to the employment of any aluminum halide as acatalyst in eifecting the condensation of cyclohexene with an aromatichydrocarbon. For instance, when cyclohexene and benzene, in a givenmolecular ratio, are reacted, at a given temperature and in the presenceof aluminum bromide as catalyst, to form monocyclohexylbenzene, -theyield of the latter is highest when between about 0.02 and about 0.25mol of aluminum bromide per mol of cyclohexene is used.

As might be expected, a mixture of isomeric monocyclohexyl aromatichydrocarbons is frequently formed when cyclohexene is reacted with anaromatic hydrocarbon containing one or more substituents, and suchmixture of isomeric products often can be separated only with extremediiiioulty. The yields of monocyclohexyl products set forth in the tableof examples represent,

in many instances, the yields of such mixed isomers. Benzene, of course,formsbut a single monocyclohexyl product.

. The following monocyclohexyl-aromatic hydrocarbons, set forth in thetable of examples, are new compounds or mixtures of isomeric newcompoundsz-a mixture of isomeric monocyclohexyl-para-chlorodiphenylsboiling at between about 193 and about 203 C. under 2 millimeterspressure; a mixture of monocyclohexyl-alphachloronaphthalenes boiling atbetween about 165 and about 185 C. under 2 millimeters pressure; amixture of. isomeric mono-cyclohexyl-orthochlorotoluenes boiling atbetween about 115 and about 117 C. under 3 millimeters pressure; amixture of isomeric monocyclohexyl-ortho-dichlorobenzenes boilingatbetween about 134 and about 137 C. under 3.5 millimeters pressure; amixture of isomeric monocyclohexyl-naphthalenes boiling between about162 and about 175 C. under 5 mililimeters pressure; and a mixture ofisomeric monocyclohexyl-diphenyls boiling at between about 155 and 186C. under 3 millimeters pressure.

From the mixtureof isomeric monocyclohexyl diphenyls we have separated,through a series of fractional crystallization and fractionaldistillation steps, a monocyclohexyl-diphenyl (probably4-cyclohexyl-diphenyl)' melting at about 76.6-77.6 C. and boiling atabout 169-171 C. under 3 millimeters pressure. Throughsimilar procedurewe have separated from the mixture of isomeric monocyclohexylpara-chloro diphenyls (1) a monocyclohexyl para-chloro-diphenyl meltingat about 55 C. and boiling at about 197199 C. under 4.5 millimeterspressure, and (2) an isomeric compound melting at about 143.6-144.6 C.and boiling at about 200 C. under 3 millimeters pressure. In similarmanner we have separated, from the mixture of isomeric monocyclohexyl-naphthalenes (1) an isom'er melting at about 30.2-31.4 C., said isomerbeing probably alpha-cyclohexyl-naphthalene, and (2) an isomer meltingat about 150-152 C., the latter beingprobably'beta-cyclohexyl-naphthalene. Allof the solid isomers isolatedwere obtained in the form of silver-colored, leaf-like crystals.

Thepresent invention, in brief, comprises. re-- acting cyclohexene withan aromatic hydrocarbon 1 or chlorinatedaromatic hydrocarbon in thepresence of between about 0.02 and about 0.25 mol of aluminum' chlorideper mol of cyclohexene used.

Other modes of applying the principle of our invention may be employedinstead of those explained, change being made as regards the method andproducts herein disclosed, provided the means stated by any ofthe-following claims or the equivalent of such stated means be employed.

We therefore particularly point out and distinctly claim as ourinvention:

1. The improvement in the method of preparing a mono-cyclohexyl-aromaticcompound which comprises reacting cyclohexene with a compound selectedfrom the class consisting of aromatic hydrocarbons and chlorinatedaromatic hydrocarbons in the presence of about 0.05 mol of an aluminumhalide per mol of cyclohexene employed in the reaction.

2. The method of making a monocyclohexylaromatic compound whichcomprises reacting a cyclohexene with a compound selected from the classconsisting of aromatic hydrocarbons and chlorinated aromatichydrocarbons in the pres-' ence of about 0.05 mol of aluminum chloridefor each mol of cyclohexene used.

3. The method of making a monocyclohexyl chlorobenzene whichcomprises'reacting cyclohexene with chlorobenzene in the presence ofabout 0.05 mol of aluminum chloride for each mol of cyclohexene used.

